A3

A3, A03 or A.III may refer to: A3 paper, a paper size defined by ISO 216

==Biology == A3 regulatory sequence, a sequence for the insulin gene Adenosine A3 receptor, a human gene Annexin A3, a human gene ATC code A03 Drugs for functional gastrointestinal disorders, a subgroup of the Anatomical Therapeutic Chemical Classification System Brachydactyly type A3, a disease British NVC community A3 (Spirodela polyrhiza - Hydrocharis morsus-ranae community), a British Isles plants community Gibberellin A3, a plant hormone HLA-A3, a Human MHC Serotype HLA-A Subfamily A3, a rhodopsin-like receptors subfamily Urea transporter A3, a trans-membrane protein